Contact Analysis for Coupling of Plates and Screws in Fracture Fixation of Cortical Bone

Internal fixation is a common treatment for bone fracture. Bone fracture occurs due to different reasons such as motor vehicle accidents, falling,…etc. The treatment is performed by fixing plate and screws to the fracture site. Lack of stability of the implants (plates and screws) may lead to delay in healing or failure of treatment. Micro-motion between the implant and the bone may cause formation of fibrous tissue around the screw which will lead to implant loosening. On the other hands, firm fixing of the conventional implants (Dynamic Compression Plates) may lead to delay resorption and delay in healing. Recently, Locked Compression Plates were introduced to get over the shortcomings of the existing Dynamic Plates. In Locked Plates the hole and screw head were threaded to provide more stability and reduce contact with the bone surface. In this communication we conducted computational analysis to compare the stability of both sets of implants. Results have revealed that Locked Plates provide more stable fixation and resistance to micro-motion. However, stress shielding might occur which will delay healing. Future designs of the Locked Plates can focus on improving stability and reducing damage to blood supply which will shorten the healing period. Computational analysis (finite element analysis) can be effectively used to guide these future designs

Commande et supervision des installations à sources renouvelables (photovoltaïque…)

Dans ce papier nous analysons la fiabilisation des installations photovoltaïques en termes de production de l’énergie électrique produite et intervention à distance. Nous proposons un système qui permet de contrôler le fonctionnement à distance par SMS. Ce système est basé sur l’utilisation et la programmation d’un microcontrôleur qui envoi et reçoit, via une liaison RS232, des commandes de suivi et d’alerte par le modem 3G. Les premiers résultats montrent le bon fonctionnement de chaque bloc du système mis en place et la communication entre ce système et l’opérateur via SMS, en temps réel, pour alerter un éventuel dysfonctionnement, marche, arrêt et transfert des données de l’installation (courant, tension, puissances, rendement…)

Studies on a multi-stage solar desalination plant (MSD)

A solar desalination system composed of an evaporation/condensation chamber formed by a lower basin and eight horizontal stages, coupled with a field of four flat thermal collectors with a total surface of 8.4 m2 and a field of panel to supply a pump, which supplies system with saline water from wells was installed in Douar Al Hamri, in the rural commune of Boughriba of the Province of Berkane and tested under the meteorological conditions of this region. A simulation model of the desalination system has been developed and validated with experimental measurements of the system. The simulation model uses a numerical solution to a set of differential equations describing the system. The objective of this installation is to produce pure (drinking) water, from a well of high conductivity (4050 µs/cm) and salt content (>2,720 mg/L), to the inhabitants, isolated and not connected to the national drinking water network. The experimental results of the MSD system show, during season of 2020, under an irradiance and ambient temperature condition of Oriental region, maximum values of the stage temperatures of  90°C and maximum production of 48 litres with low conductivity (88 µs/cm) and salt content (<0.045 mg/L).  The main objective of this pilot station in Morocco is to ensure the production of drinking water to the inhabitants of the Douar by solar energy. The modelling of these experimental results, from the thermal equations, set up during this work, shows a very good agreement between the experiment and the simulations. The analysis of all the results and their comparisons with the literature clearly show the good functioning of the MSD system blocks, set up during this work.

Operation of Photovoltaic Panels in Stand-alone Applications

In this chapter, we propose the analysis of the maximum power point (MPP) of photovoltaic panels (PV) in a renewable energy application. From the current–voltage characteristics, we deduced the MPP of a PV panel and specified the use of a power block (DC/DC converter) controlled by an MPPT control. In the case of an MPPT control of type perturb and observe, we realized the photovoltaic system that heats a photovoltaic solar cooker, taking into account this MPPT command. The experimentation of this application, during a sunny day, shows that the MPPT control carries out its role correctly, such as optimal operation of the PV panels and heating of the cooker by the maximum power supplied by the PV panels. The analysis of all the results shows an excellent agreement between the experiment and the simulation of the operation of the photovoltaic system which made it possible to operate the photovoltaic panels around their MPP, over the course of the sun. Under these conditions, the efficiency of the proposed DC/DC converter, with a power of 500 Wp, is of the order of 97%

Dynamics of Lennard-Jones clusters: A characterization of the activation-relaxation technique

The potential energy surface (PES) of Lennard-Jones clusters is investigated using the activation-relaxation technique (ART). This method defines events in the configurational energy landscape as a two-step process: (a) a configuration is first activated from a local minimum to a nearby saddle-point and (b) is then relaxed to a new minimum. Although ART has been applied with success to a wide range of materials such as a-Si, a-SiO2 and binary Lennard-Jones glasses, questions remain regarding the biases of the technique. We address some of these questions in a detailed study of ART-generated events in Lennard-Jones (LJ) clusters, a system for which much is already known. In particular, we study the distribution of saddle-points, the pathways between configurations, and the reversibility of paths. We find that ART can identify all trajectories with a first-order saddle point leaving a given minimum, is fully reversible, and samples events following the Boltzmann weight at the saddle point.Comment: 8 pages, 7 figures in postscrip

Prevalence of diabetes complications in people with type 2 diabetes mellitus and its association with baseline characteristics in the multinational A1chieve study

BACKGROUND: Current International Diabetes Federation guidelines recommend a target HbA(1c) <7.0%, but many people with diabetes worldwide find this difficult to achieve, increasing their risk of developing complications. This publication examines the prevalence of diabetes complications and its association with baseline characteristics in people with type 2 diabetes who participated in the A(1)chieve study. METHODS: A(1)chieve was a 24-week, multinational, open-label, observational study of 66,726 people with type 2 diabetes who had begun using biphasic insulin aspart 30, insulin aspart, or insulin detemir in routine clinical care. Participants were enrolled from 28 countries across four continents (Asia, Africa, Europe and South America). Baseline measurements of disease characteristics included: glycated haemoglobin (HbA(1c)), fasting (FPG) and post-prandial plasma glucose (PPG), high- and low-density lipoprotein cholesterol (H- or LDL-C), systolic blood pressure (SBP), and body mass index (BMI). Data on complications and use of vascular disease preventative drugs were collected. RESULTS: Complication rates were high (27.2% had macrovascular complications and 53.5% had microvascular complications), particularly in Russia, and use of vascular disease preventative drugs was lower than expected. Age, BMI, diabetes duration, LDL-C, and SBP were positively associated, and HDL-C negatively associated, with macro- and microvascular complications (all p < 0.05). HbA(1c) and FPG were negatively associated with macrovascular complications (both p < 0.05), which may be linked to the cross-sectional study design. CONCLUSIONS: These results suggest a worldwide failure to achieve glycaemic targets. Better diabetes management with earlier initiation and optimisation of insulin regimens (e.g., with insulin analogues in the A(1)chieve population) may reduce the prevalence of vascular complications, improve the lives of people with diabetes and reduce the burden on healthcare systems

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10&nbsp;years; 78.2% included were male with a median age of 37&nbsp;years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020